PostgreSQL - Campo timestamp sem milissegundos

CREATE OR REPLACE FUNCTION self_destroy() RETURNS void AS
$BODY$
BEGIN
DROP TABLE IF EXISTS mslxp_self_destroy;
CREATE TEMP TABLE mslxp_self_destroy
(
dt1 timestamp    without time zone,
dt2 timestamp(0) without time zone
);
INSERT INTO mslxp_self_destroy(dt1, dt2) VALUES (clock_timestamp(), clock_timestamp());
DROP FUNCTION self_destroy();
END;
$BODY$
LANGUAGE plpgsql;

SELECT self_destroy();
SELECT * FROM self_destroy;

Resultado:
2012-05-18 11:10:03.414 | 2012-05-18 11:10:03